This blog was originally started to better help me understand the technologies in the CCIE R&S blueprint; after completing the R&S track I have decided to transition the blog into a technology blog.

CCIE #29033

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Saturday, April 24, 2010

Question 17

When to use OER?

1 comments:

Packets Analyzed said...

OER - Optimized Edge Routing allows you to route traffic outbound to multiple service providers intelligently. OER can determine black or brown outs within the service provider network that may include service disruption or packet loss, once detected OER can route around the problem. Normal routing is based on the routing path as opposed to the condition of the path. OER policy violations include response time, packet loss, path availability, and traffic load distribution. OER requires a master controller and border routers. OER can influence routing by setting the local preference in BGP or by creating a static route for a specific prefix. Route changes on the border routers influence internal routers in the internal network by either internal BGP peering or BGP/Static redistribution into the IGP.

The state prefixes go through once learned are
-default, this is the start state and is not in OER control
-In-Policy, matches default or configured policy. No changes
-Out-of-Policy, does not match and is looking for a better route. Master controller chooses best one.
-Choose, Master controller is selecting new exit link
-Holdtime, new exit link has been selected by the master controller. No changes to the policy during the holdtime. Prevents route flapping

OER can run in two modes which includes "observe mode" (OER does not make routing changes but makes recommendations by show commands or syslog) and "control mode" (makes changes to the routing).

Cisco OER requires CEF (Cisco Express Forwarding), consistent routing, and redistribution of static routes into your IGP.

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